Velocity modulation device having a coaxial output



B. C. WINTERS July 12, 1966 VELOCITY MODULATION DEVICE HAVING A COAXIAL OUTPUT 2 Sheets-Sheet 1 Filed July 2, 1962 INVENTOR.

ATTORNEY BE/PL C. VV/NTERS United States Patent 3,260,886 VELOCITY MODULATION DEVICE HAVING A COAXIAL OUTPUT Ber] C. Winters, Gainesville, Fla., assignor to Sperry Rand Corporation, Great Neck, N.Y., a corporation of Delaware Filed July 2, 1962, Ser. No. 206,628 8 Claims. (Cl. 315-5.38)

This invention relates to electron discharge devices, and more particularly to output coupling structures for velocity modulation devices.

In many modulation devices of the k-lystron type, electromagnetic oscillations at microwave frequencies are developed in a toroidal cavity resonator that is aligned coaxially with the tube body. Microwave energy is cou pled to exterior utilization means through a rectangualr wave guide disposed radially with respect to the tube so that the axis of the wave guide is perpendicular to the axis of the k-lystron. The lines of electric flux near the outer cylindrical wall of the cavity are parallel with each other and therefore so oriented that an output iris in this wall permits the field in this region to be coupled directly to the output wave guide.

Radially disposed wave guide feeds are cumbersome, however, and this type of feed cannot be tolerated in many applications in which space is at a premium.

Klystrons with axial wave guide outputs have been built in which the components are so arranged that the internal electron beam is caused to flow along a diameter of the tube body. This artifice permits a conventional type radial output iris to be used to provide an axial output, however it requires that the electron beam geenratiug andcollecting components be aligned radially in the tube body. This arrangement, in turn, necessarily restricts the size and power handling capability of the components if the tube body is to be limited to reasonable dimensions. Furthermore, this type of tube is not sufficiently rugged to withstand the severe mechanical shocks encountered in some applications.

It is an object of the present invention to provide a compact velocity modulation type tube with an axial wave guide output.

It is another object of the present invention to provide a compact velocity modulation type tube that can withstand severe mechanical shock.

It is still another object of the present invention to provide a velocity modulation type tube that can be coupled directly to an axially disposed exterior wave guide with no intermediate cavities or wave guide sections.

These and other objects are accomplished in the present invention by coupling energy to an output wave guide by means of radial voltage components induced in an iris in the transverse wall of a toroidal cavity.

The invention will be described with reference to the following drawings wherein:

FIG. 1 is a perspective view of a tube constructed according to the principles of the present invention,

FIG. 2 is a view, partly in cross section, illustrating a preferred embodiment of the invention,

FIG. 3 is a cross sectional view taken along the line 3-3 of FIG. 2, and

FIG. 4 is a cross sectional view taken along line 44 of FIG. 2,

Referring now to FIG. 1, a klystron tube body 11 includes a transverse end portion 13. A rectangular wave guide 15 may be mounted on the klystron tube body as indicated, by suitable mounting means such as the tapped holes 17. Energy is coupled into the wave guide through suitable coupling means such as the conventional wavepermeable output window 19.

Referring now to FIGS. 2, 3 and 4, there is shown a two-cavity klystron constructed according to the principles of the invention. A means for generating an electron beam such as a conventional electron gun 21 is arranged to provide an axial beam of electrons that passes through an annular sleeve 23 and impinges on the collector element 25. A hollow conductive cylinder 27 together with a metallic collector disc 29 and an apertured end section 31, form a conductive shell that defines an elongated cylindrical chamber 33. A metallic partitioning member 35 is fabricated in the form of an annular disc supporting the sleeve 23 and serving to divide the chamber 33 into a toroidal input cavity resonator 37 and a toroidal output cavity resonator 39. A feedback coupling iris 41 serves to couple energy from the output cavity back to the input cavity. As is well known in the art, an electron beam flowing between the electron gun 21 and the collector element 25 in such an arrangement can induce electromagnetic oscillations in the resonant cavity. The frequency of such oscillations is determined by the physical dimensions of the cavities. Tuning screws 43 can be used to deform the cavity walls in order to provide tuning.

Conventional tubes of the type under consideration usually couple energy from the output resonant cavity to an external wave guide through an iris in the cylindrical cavity wall where the lines of electric flux of the electromagnetic field are substantially parallel. The present invention, however, utilizes energy coupled out of the resonant cavity 39 by means of an output iris 45 in the collector disc 29 even though the electric flux lines established in the iris from this region of the cavity are divergent rather than parallel. The output iris 45 is preferably constructed in the form of an arcuate slot in the inner face of the collector disc 29 as best shown in FIG. 3. The inner wall 47 of the coupling iris is outwardly tapered as best shown in FIGS. 2 and 4 so as to intersect the outer face of the collector disc in a curve 49 that approximates a conic section.

The electric flux lines associated with the microwave field that enters the iris 45 are radially disposed around the axis of the cavity. The tapered iris wall functions as a transition section within the iris itself tending to transform the field from the cavity into a field having parallel flux lines.

Such a field is suitable for launching a wave in the dominant mode in a. rectangular wave guide mounted with its broad walls perpendicular to the axis of symmetry of the arcuate slot as indicated by the dashed lines in FIG. 4.

As presently employed, an iris in the form of an arc of about gives adequate coupling. The exact physical dimensions, however, are a matter of choice in design and depend upon such factors as the power level of the tube and the shape of the particular resonant cavity.

Although an iris in the shape of an arcuate slot with an outwardly tapered wall is presently preferred, variations in this particular configuration can be accommodated.

The invention is primarily concerned with means for launching energy in the dominant mode in a rectangular wave guide, however the same principles may be employed to excite higher order modes in both rectangular and circular wave guides. Thus, for instance, the collector disc 29 may contain two diametrically opposed irises and be used to excite a variety of higher order modes in appropriate wave guides.

Velocity modulation devices containing other than two cavities may use the principles of the present invention. Thus single cavity reflex klystrons can be designed with a transverse iris in a manner simiar to that described for the two cavity klystron.

Furthermore, although the invention has been described for use in velocity modulation devices operating as oscillators, the same type of axial output coupling iris can be used in such velocity modulation devices operating as amplifiers.

While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than of limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

1. A velocity modulation device comprising a tube body, a flat wave-permeable window in one surface of the tube body, a toroidal cavity resonator mounted within the tube body, and a collector disc forming a transverse wall of the toroidal cavity resonator parallel to the wave-permeable window, said collector disc containing an output iris in a region beneath said window.

2. A velocity modulation device comprising an elongated body, a transverse end portion on the body, a Wavepermeable window in said end portion, a toroidal cavity resonator mounted within the body, said toroidal cavity resonator containing an output iris in a region of radially divergent electric flux, said iris lying in a transverse plane adjacent said window whereby electromagnetic energy may be propagated in an axial direction toward said output window.

3. A klystron comprising an elongated tube body, a transverse end portion on the tube body, a wave-permeable output window in said end portion, means for generating an electron beam in an axial direction within said tube body, and a collector disc defining a transverse cavity wall and containing an output iris, said collector disc having an inner and an outer face, said outer face lying adjacent to said output window, said output iris including an arcuate slot in the inner face of the collector disc, said output iris further including an outwardly tapering wall intersecting the outer face of the collector disc in a conic section.

4. A velocity modulation device comprising means for generating an electron beam, a hollow conductive shell defining a cylindrical chamber, an axially aligned annular sleeve positioned within said chamber so as to be traversed by the electron beam, a transverse partitioning member supporting the annular sleeve, a transverse collector disc containing a concentric collector element and an output iris, energy coupling means adjacent to said output iris, said partitioning means cooperating with the conductive shell to form a resonant cavity, a tube body for housing the velocity modulation device, and wave guide mounting means on said tube body for attaching an output wave guide with its axis collinearly aligned with the axis of the electron beam, said output iris being constructed in the form of an annular slot whereby electromagnetic energy can flow in an axial direction from the resonant cavity to the energy coupling means. 5. A velocity modulation device comprising means for generating an electron beam, a hollow conductive shell defining a cylindrical chamber, an axially aligned annular sleeve positioned within said chamber so as to be traversed by the electron beam, a transverse partitioning member supporting the annular sleeve and serving to divide the chamber into input and output resonant cavities, a transverse collector disc forming one end of said conductive shell, an electron beam collecting element, said collector disc supporting the collector element and containing an output iris, a wave-permeable output Win-.

dow adjacent to the output iris, and wave guide mounting means for attaching an output wave guide over the output window with its axis collinearly aligned with the axis of the electron beam, said output iris being constructed in the form of an elongated slot oriented so that the edges of the slot are normal to the adjacent electric flux lines formed during operation of the cavity.

6. A klystron tube comprising:

(a) an elongated body,

(b) a transverse end portion on the body,

(c) an output window arranged concentrically in the transverse end portion,

(d) an electron gun within the body arranged to project a beam of electrons axially toward said window,

(e) a concentric collector means adjacent to the inner side of said window arranged to intercept the beam of electrons from the electron gun,

(f) a conductive shell defining an elongated cylindrical chamber arranged to be traversed by said electron beam,

(g) a transverse collector disc supporting said collector means and forming one end of said'elongated chamber,

(b) said collector disc containing an output iris in the form of an arcuate slot disposed along an annulus about the collector means, and

(i) means for mounting an external rectangular wave guide over the output window so that the axes of the wave guide and the tube body are collinear and so that the broad walls of the wave guide are perpendicular to the axis of symmetry of the output iris.

7. A klystron tube comprising:

(a) an elongated body,

(b) a transverse end portion on said body,

(c) means for coupling an external wave guide to the klystron so that the axes of the klystron and the wave guide are collinear,

(d) an output window in said end portion,

(e) an electron gun within said tube body oriented to project a beam of electrons axially toward said window,

(f) a concentric collector means adjacent to the inner side of said window arranged to intercept the beam of electrons from said electron gun,

(g) a transverse collector disc supporting said collector means and containing an output iris,

(h) a hollow conductive cylinder surrounding said collector disc and extending axially toward said electron gun,

(i) a transverse partitioning member inside said cylinder,

(j) said collector disc, conductive cylinder, and partitioning member forming an output resonant cavity,

(k) said output iris being formed as an elongated slot disposed along an annulus about said collector means whereby microwave energy can be coupled in an axial direction from said resonant cavity directly to an external wave guide.

8. A klystron tube comprising:

(a) an elongated body,

(b) a transverse end portion on said body,

(0) means for coupling an external wave guide to the klystron so that the. axes of the klystron and the wave guide are collinear,

(d) an output window in said end portion,

(e) an electron gun within said tube body oriented to project a beam of electrons axially toward said window,

(f) a concentric collector means adjacent to the inner side of said window arranged to intercept the beam of electrons from said electron gun,

(g) a transverse collector disc supporting said collector means and containing an output iris,

(h) a hollow conductive cylinder surrounding said collector disc and extending axially toward said electron gun,

(i) a transverse partitioning member inside said cylinder,

(j) said collector disc, conductive cylinder, and partitioning member forming an output resonant cavity,

(k) said collector disc having inner and outer faces,

(I) said output irisbeing shaped to form an arcuate slot in the inner face of the collector disc,

(m) an outwardly tapering wall in said iris, intersecting said outer face in a conic section.

References Cited by the Examiner UNITED STATES PATENTS 2,826,713 3/1958 Hernquist 31539 DAVID J. GALVIN, Primary Examiner. GEORGE N. WESTBY, Examiner. V. LAFRANCHI, Assistant Examiner. 

1. A VELOCITY MODULATION DEVICE COMPRISING A TUBE BODY, A FLAT WAVE-PERMEABLE WINDOW IN ONE SURFACE OF THE TUBE BODY, A TOROIDAL CAVITY RESONATOR MOUNTED WITHIN THE TUBE BODY, AND A COLLECTOR DISC FORMING A TRANSVERSE WALL OF THE TOROIDAL CAVITY RESONATOR PARALLEL TO THE WAVE-PERMEABLE WINDOW, SAID COLLECTOR DISC CONTAINING AN OUTPUT IRIS IN A REGION BENEATH SAID WINDOW. 